Have you re-downloaded the most current Avast? Probably yes. Registering only means sending them your email address. I've never had protection ever stopped, but maybe they do. I've used Avast for many years because I'm a builder, and it's a decent AV program provided by a marketing company. Never forget that. The last time I downloaded it, it didn't even prompt me to register it which is why I asked that question first. The free program is equal to the paid program for AV protection. If you're not covered with Avast then Windows Defender will be active. Go to Task Manager and see if Avast is running. If so, then all you have to do is ignore the ads from them. If not, then search online on how to remove it completely and then re-download and install...or go with AVG Free, or McAfee, or a dozen others that do the same things and let them just override Avast.